The invention disclosed herein relates to an electrical connector for making electrical connection to at least one electrical conductor, particularly for connecting a conductor without stripping the insulation therefrom, and especially as used for telecommunications applications.
There are many different terminal blocks currently available for use in the telecommunications field, each aiming to fill a specific need. Most, however, are relatively old and are labor intensive to install and maintain. They also suffer from a variable signal quality as they are open to the elements and corrosion build-up degrades the signal.
In typical usage in telecommunications applications, a telephone distribution cable is permanently attached to a terminal block at manufacture and spliced into the telecommunications system at installation. The connections to the terminal block vary from 26 gage vinyl insulated copper wire to rubber insulated copper coated hard steel "drop wire" or "drop line" that runs from a pole or pedestal to the house connection. (A typical drop wire has a pair of conductors in a single jacket linked like electrical lamp cord.)
A current terminal block is disclosed in Debruycker U.S. Pat. No. 4,846,721. Such a terminal block, and blocks based on it, have several disadvantages. They cannot accept a drop wire "pair" without the installer first splitting the two conductors. Also, because of the method of connection and the materials used, the hard steel drop wire frequently deforms the contacts in the terminal block upon tightening. While such blocks maintain good contact with the initial connection, they are not capable of then making connection to a lighter gage conductor.
In order to maintain a waterproof connection, the joint in connectors of terminal blocks may be protected by a water resistant compound, such as a gel or grease. In conventional connectors, the connection actuator acts like a tight fitting piston in a cylinder so that as the connection is made tighter the available volume in the cylinder is decreased. As the gel or grease is not compressible, an escape relief is provided for the excess material. That means that the material must move almost completely out of the initial cylinder into the relief area and still be able to return when the connection is loosened. This is very difficult for a grease to accomplish so that gels are required.
Most of the terminal blocks currently available employ either screws with washers or studs with nuts and washers to make removable outside connections. In either case, the insulated connector must be stripped and then is tightened between the washers to make the connection. These connections can accommodate a large range of wire sizes and make good electrical contact consistently. However they do require preparation of the wire and are very difficult to protect from atmospheric corrosion.
Connections may also be made without stripping insulation from the conductors. Many connectors which require and connect unstripped conductors displace the insulation to make electrical connection to the conductor.
There are two general classes of such insulation displacement connectors. In one type, the connector includes a blade with a tapered slot. The wire is pushed into the slot and the edges of the slot pierce the insulation and make contact with the conductor. This type is widely used for inside connections when the conductor size range is very narrow. The disadvantages are the inability to handle more than one or two conductor gage sizes and the lack of atmospheric protection. In many areas of the country this type of connector is no longer used because of problems with corrosion attacking the electrical contact locations. The second type connector uses a special capped nut that fits over a threaded stud with a cross hole for the conductors. A single conductor is inserted into the cross hole and the cap tightened to a stop. The conductor is pinched between the edge of the cross hole and the edge of the cap making electrical contact through the insulation. The entire mechanism is buried inside the terminal block and protected with a waterproof grease or gel. To fit the full range of wire sizes it is necessary to maintain very tight dimensional control of the components which make those terminals expensive. They do work however and in Applicant's estimation are the best terminal blocks now on the market. They have disadvantages in that they are inherently expensive, in that the drop lines or conductors usually manufactured as joined pairs must be separated, but not stripped, before being terminated, and that only one conductor can be terminated at a time.